Spotfire is an application built around S-Plus that has widespread use
in the biopharmaceutical industry at a minimum. Vivek Ranadive's
TIBCO company just purchased Insightful, the S-Plus company.
(They bought Spotfire previously.)
Mr. Ranadive does not spend money on environments that are
not appropriate for deploying applications.

You could easily cull a list of corporation names from the
various R email listservs as well.

Press back with the reviewer. Reviewers can learn new things
and will respond to arguments with good evidence behind them.
Good luck!

I got the following comment from the reviewer of a paper (describing an
algorithm implemented in R) that I submitted to BMC Bioinformatics:

"Finally, which useful for exploratory work and some prototyping,
neither R nor S-Plus are appropriate environments for deploying user
applications that would receive much use."

I can certainly respond by pointing out that CRAN contains more than
2000 packages and Bioconductor contains more than 350. However, does
anyone have statistics on how often R (and possibly some R packages) are
downloaded, or on how many people actually use R?